> the stellar mass density is affected by two processes: star formation and star destruction Hang on, it sounds like you're talking about the total stellar mas

> the stellar mass density is affected by two processes: star formation and star destruction Hang on, it sounds like you're talking about the total stellar mass, not density. I'm not an astronomer, but assuming they use the normal definition of "density" there are two things that affect it: total stellar mass (which, as you said, can be further broken down into formation and destruction) and the volume it's contained within. Isn't the universe expanding? (Again, I'm not an astronomer.) If the density is going to remain similar to now then that means that the total stellar mass is going to continue increasing too. That's consistent with what your comment literally says but is quite different from how I think most people would interpret it.